"Zombie" light bulbs

[ppppenguin]

Circuit capacitance can make it impossible to switch off some LED lamps:
https://www.youtube.com/watch?v=1uEmX5XClPY

I've read about CFL lamps that flash slowly when switched off due to the reservoir capacitor charging via wiring stray C.

Apart from adding some extra load (conventional filament lamp?) how do you stop this happening?

I've not witnessed either effect.

[Richard_FM]

From just reading the title I thought I would mention that I've had a power saving bulb that has faded & started to flicker but not died completely.

[pwdrive]

Put a capacitor across the bulb.

Lawrence.

[Amie]

We've had this!
pwdrive +1,

Also 470k works in lampholder

[jjl]

We have this effect with our bathroom light fitting that has 3 G9 type bulbs, fitting one halogen G9 along with two LEDs puts a stop to it. I did think that it might be caused by a faulty switch, but replacing the switch didn't change the effect.

John

[ppppenguin]

A capacitor (X or Y rated) acoss the bulbs, as suggested by Lawrence, seems like the best answer. I think I'd try 100n or whatever I had to hand and see if it works.

[Amie]

Dad said it was capacitance/leakage between the wires to the switch that caused it, it was old wiring that doesn't have ecc in it, the leakage was enough to charge the bulbs PS capacitor, a particular brand would briefly flash, once every couple of minutes.

Amie.

[ppppenguin]

Amie, that's entirely correct, at least for CFL bulbs. For LEDs it looks like enough current flows though the stray C to make it light up.

I'm not sure that the earth conductor makes much difference. There will still be stray C between the 2 other cores. Even worse on a 2 way switched circuit where there is more cable and hence more C.

[Kalee20]

Agree Amie, the leakage allows enough current to slowly charge the power supply capacitor in the lamp, up to the point where there is enough charge to trigger the lamp to run.

Then, the running lamp quickly discharges the capacitor and the lamp goes out... Repeated ad infinitum!

[ppppenguin]

Just like the neon bulb flashers that many of us older guys built years ago. Just a 90V battery, series R, parallel C and neon.